This invention concerns radio frequency identification tags to be used as identifiers and for counting and inventorying articles and containers of articles. In particular, the invention concerns a miniature RF ID tag generally of the type disclosed in U.S. Pat. No. 6,480,699, which is incorporated herein by reference.
Radio frequency ID tags have been described in various forms, and designed for various purposes. The type of ID tag to which this invention is concerned essentially comprises an integrated circuit with an antenna onboard the chip, and with an energy store which will capture a portion of the RF energy from an interrogator unit, store that energy and use it to power a responding signal transmitted from the tag, as in U.S. Pat. No. 6,480,699.
Currently, in the manufacture of semiconductor devices (for a variety of different purposes, not only ID tags) dice are tested by connecting each die individually with a tester. This typically occurs while the dice are still on the wafer and also after each die has been cut from the wafer and assembled, and it is a costly procedure.
In addition, present semiconductor devices typically are pre-tuned by automatic testing equipment (ATE) during a manufacturing test. Such devices are often tested/tuned numerous times in both the wafer stage (before packaging) and in a final test (wherein the device is packaged). To eliminate any high variation in the manufactured devices, a fairly expensive process with narrow tolerances is required for the initial tuning. Most fine tuning of semiconductor devices cannot make adjustments over a wide enough range to overcome the initial production offset, unless ATE type pre-tuning has been performed. There is a need for a less expensive regime for tuning of semiconductor devices to target values, particularly in the production of RF ID tags. ATE type testing is expensive and its avoidance is an object of the invention. It would be desirable to perform as much testing of RF ID tags as possible at the time of application of the tags, rather than during manufacturing, although an efficient parallel test for manufacturing defects would also be desirable at the time of manufacture.
In RF ID tags, of the type described in U.S. Pat. No. 6,480,699 wherein an onboard power supply stores energy from an interrogating signal, the responsive tag transmission in many applications must occur in a specific time slot which is distinct from the transmit time slots of all other tags similarly situated. This is needed for collision avoidance, that is, simultaneous responsive transmissions from multiple tags. This is true for applications in which a large number of items are to be detected, counted, tracked and/or identified, since the reader needs to detect or count or track or identify every individual item. U.S. Pat. No. 6,480,699 described a method to reduce data transmission collisions from RF ID tags by having each tag select a random time slot. This would require each of the tags to have an onboard random number generator as well as supporting digital circuitry to calculate the random time slot in which to transmit. It would further economize the production of semiconductor RF ID tags to eliminate the need for such onboard random number generators and supporting circuitry, by imposing a random time slot on each tag in a different way.
Different nations of the world have different regulations regarding frequency bands for radio frequency devices. This requires RF ID tags to be tuned differently for different jurisdictions. It would be efficient and highly desirable to be able to produce a single form of tag which is tunable to an appropriate frequency for the requirements of all applicable jurisdictions. In addition, even within a single jurisdiction, different frequencies are often needed for different applications, within the same facility, for reasons relating to interference and false readings for different products or applications. A tunable tag, tunable by the user at time of application, would allow for the production and inventorying of only one type of tag, again saving cost and increasing efficiency.
The following U.S. patents have relevance to the invention described below: U.S. Pat. Nos. 6,480,699 and 6,825,683.
It is among the objects of the invention to address the needs described above. These and other objects, advantages and features of the invention will be apparent from the following description of preferred embodiments, considered along with the accompanying drawings.